UKCP09 updates

Guidance for Spatially Coherent Projections - November 2010

We have developed guidance pages for About the Spatially Coherent Projections (SCPs) by applying scaling factors to the 11-member RCM ensemble in order to incorporate more of the uncertainties available through UKCP09. This is useful for users who require spatial coherency in the data but would also like to explore the more robust range of uncertainty available through UKCP09. The results make explicit a wider range of uncertainty than the 11-member RCM but still include 11 equally plausible projections of future climate.

It is important to note, however, that SCPs are not a replacement for UKCP09. They should be used in conjunction with the full set of UKCP09 probabilistic projections. The SCPs under-sample uncertainties in UKCP09, but explore a wider range of uncertainties than the RCM.

Maps of probability for a given threshold added - November 2010

Maps for the UK can now be produced to show the projected probability, across the UK, of a relative user-defined threshold. They are available for download from the UKCP09 User interface. This is useful for UK-wide activities with known thresholds.

Technical notes available - November 2010

Technical notes on fog, lightning and snow have been added to the 11-member RCM pages. Summaries are provided below for the 2080s under a Medium emission scenario.

Fog - Generally reductions across all seasons.

Lightning - Increase in the number of lightning days across the UK for all seasons.

Snow - Mean of the ensemble shows reductions in snow days in all regions. The general pattern of heavy snow events shows large reductions, but with greater intra-ensemble uncertainty.

Probabilistic information for wind speed - November 2010

Probabilistic projections for wind speed are now available from the UKCP09 .csv archive (raw data). They show that the Central estimates of change are small in all cases (< 0.2 ms-1).

Projected changes in Winter wind speed are approximately symmetrical around near-zero change. In the Summer, it is slightly skewed towards negative in the UK and slightly positive in Scotland under the Medium emission scenario for the 2050s.

Uncertainties (10%-90% probability range) typically in the range 5-20% of the present day climatological mean, are dependent on future period, emissions scenario and location.

Natural climate variability contributes much of the uncertainty. The modelling captures several feedback mechanisms that could affect winds and storms over the UK. However, these models do not resolve stratospheric processes very well. Early results from newer models suggest an additional feedback process when the stratosphere is included, which could affect projections of wind and precipitation in winter and spring. More work is needed to determine the magnitude and robustness of this effect.

Several of the models going into IPCC AR5 will include a higher resolution stratosphere, so the implications for UKCP09 will become clearer during the next couple of years.

A
Technical note [119kb] that summarises the information available on storms in UKCIP02, UKCP09 and selected other sources was added. Different publications can define storms differently and so readers must be clear how a storm is being defined.